feat: add workspace-isolated toolhost runtime and capability-gap skill loop

internal/toolhost/stdio.go

@@ -0,0 +1,14 @@
+package toolhost
+
+import (
+	"io"
+	"os"
+)
+
+func stdin() io.Reader {
+	return os.Stdin
+}
+
+func stdout() io.Writer {
+	return os.Stdout
+}